JTAGTest and ViaTAP are multiplatform! They work both on Microsoft Windows and Linux!

About IEEE1149.1 JTAG Test

JTAGTest is invaluable tool for all embedded designers, production houses and service companies.
JTAGTest helps you with PCB debugging, prototyping, testing and repairing.
The device pin signals or internal signals can be monitored in real-time without
interfering with normal device operation, or you can actively
change pin states.
All this is possible using an IEEE 1149.1 (JTAG) boundary-scan.